Cartilage proteoglycan alterations in an experimentally induced model of rabbit osteoarthritis

Size distribution of cartilage proteoglycans (PG) extracted from control and osteoarthritic rabbit knees after partial meniscectomy was analyzed. In normal control knees, about 30% of PG molecules were in aggregate form and average sedimentation constant was 60S. No aggregates were found in osteoarthritic cartilage, whether ulcer, rim about ulcer, or distant normal-appearing cartilage was examined. Weight average sedimentation constants for PG subunits were similar to controls, 15S. Up to 70% of guanidinium-extractable PG could be extracted from osteoarthritic cartilage by using 0.5M guanidine HC1 (GuHCl); sedimentation characteristics of extracted PG were similar to those using 4.0M GuHCl. Absence of aggregates is consistent with a disorder of link protein, hyaluronic acid, or PG subunit hyaluronic acid binding sites. Absence of subunit degradation was an enexpected finding. The demonstrated ability of 0.5 M GuHCl to extract large amounts of PG from osteoarthritic cartilage will allow study of cartilage proteoglycans in their native nondissociated state.